What are the advantages and disadvantages of self-pollination and cross-pollination?

Answer 1

Self pollination does not require pollinating agency and it is accompalished with lesser amount of material (pollen grains) but selfpollination leads to homozygosity and sometimes sterility due to lethal genes.

Cross pollination helps in genetic advancement and evolution of hybrids and it is preferred by majority of plants. Although cross pollination reqiures plenty of pollenating material and presence of pollinators.

Answer 2

Cross pollination brings genetic diversity, which is generally good for a population's survival, but it requires pollen to get from one plant to another. Self pollination produces plants which are like the parents, which may or may not be what we want. If pollination from another source does not occur, self pollination ensures that seeds are still produced.